DAC Info This is a post to newer members on the forum who have a DVD player and wish to get better sounds from their CD playback and the option of adding a DAC to their system gives, rather than buying another CDP . This was wrote for another hifi forum but is equally at home here with all the DVD-V owners looking for a stereo sound upgrade. Apologies to all the dudes who know what DACs are but youd be surprised how many people dont know about them and just blindly purchase CDPs. What is a DAC : A DAC is a digital to analogue convertor that is generally found inside Integrated (One Box) CDPs that convert the digital signal from a CDs laser pickup to an electric analogue signal for your amplifier. Here is a better run down http://www.howstuffworks.com/cd2.htm but DACs are available in their own right as well as Int. CDPs. All you need is a CD or DVD transport to feed your DAC a signal. So in effect a DAC+Tranport is a 2 box CDP. What is a Transport : A Transport is a digital source with a digital output that can be used to feed an offboard DAC, they need to have a digital output of some sort to qualify as a transport, be it Optical Toslink, Coaxial SDif 75 ohms RCA/BNC plugged connectors or Balanced AES/XLR 110 ohms connectors. These are generally dedicated CD transports (with no analogue outputs), Int. CD players, DVD-V/A & SACD players which all are capable of playing rebdook CDs as well. Note that MD, DAT, DAB have digital outputs that send a sampling rate of 44.1 khz pcm signal like the redbook CD standard as well. These can be sent to another DAC for processing rather than listening to the units onboard (generally lesser quality) DAC. How do I hook up a DAC : Simply look at the back of your current CDP - DVD, see what type of digital output is has, then make sure the DAC your thinking of has the same connector, the most common on CDP/DVD is the RCA 75ohm Coaxial connector, then hook a 75ohm digital cable from Transport to DAC. Then like your current CDP use a set of normal ICs to take the analogue signal from DAC to Amp. What type of connections are best : The generally accepted view is that AES/XLR Balanced connection which send a 110ohm signal are the best, this type of signal is generally used in long run applications like studios, the actual benefit in home hifi is debatable. Next up is the most common : the 75 ohm Coaxial connection this comes in 2 plug types, BNC (which is the better less jittery) & the more common RCA plug (like normal ICs) this is because the RCA is not a true 75 ohm connection. Finally the Optical Toslink connection is usually regarded as the lowest quality. Although saying that, many people find Toslink pretty good. What is Jitter : http://www.digido.com/jitteressay.html or http://www.jitter.de/english/engc_navfr.html these are good places to start, but in general terms Jitter is time-base error. It is caused by varying time delays in the circuit paths from component to component in the signal path. Jitter is the main problem in CD transports to offboard DACs, Jitter is a cause of glare, harshness, lack of soundstage and loss of low level detail apparent in most CD replay systems. How can we deal with Jitter : The 2 most common ways of dealing with Jitter are : at the CD transport, where reclocking (re-timing) the data prior to output can supress jitter, check out these mods available : http://www.trichordresearch.com/cd_player_upgrades.html Or you can choose a DAC that is not as effected by jitter as others. These are generally true recovery clocking DACs which suppress jitter, by using PLLs (Phase Locked Loops) in simple terms the more PLLs a DAC uses in recovery the better it is at handling jittery input signal (and therefore is not too transport dependant). RAM buffer technology devices which effectively elminate jitter are interesting new devices which are now appearing on the market http://126.96.36.199/website/products/dac64.htm Can I make my own DAC : Yup duders http://www.tnt-audio.com/clinica/solidstate.html At what point should I use a DAC : IMHO once you go to upgrade your current Int. CDP going on to another Int. CDP means that all you are doing is paying for transport costs again your not actually getting "Sound Per Pound" Thats where the offboard DAC comes in. I think that most £300 CDP or DVD players with the addition of a DAC can really transform the CD playback of the existing transport into £1000+ territory. There are other benefits, if your transport packs in your not paying for the DAC section again when you buy another CDP. When your transport goes then adding a similar priced CDP/DVD will do the job. This Costs less in the long run. Most DACs have multiple inputs so hooking up digital sources like MD, CDR, DAB actually costs less money for expensive ICs, you cut down the need for loads of inputs on amps (ie you only need the DAC input for digital sources) further processing from digital sources to a well designed DAC will have positive effect on your other digital sources performance. Owners of existing DVD-V players should not be buying another integrated CDP until they check out DAC you will get more perfromance for your money. Whats the bad news : Well it is a 2 box solution, you will need another plug, another shelf, a digital cable and an understanding SWMBO for the DAC addiction that comes once you own one. Future DAC Dudes here are some links to DACs on the net that may come in handy in your search for info on specific DACs you may be interested in. http://www.ecoustics.com/Home/Home_Audio/DAC_and_Transports/DAC_and_Transport_Reviews/ http://www.audioasylum.com/audio/digital/bbs.html http://www.stereophile.com/showcategory.cgi?category=Digital Source Reviews Final disclaimer : Int. CDPs sound wonderful TOO !! But DACs are better IMHO !! Enjoy dudes !!